1. Field of the Invention
The present invention relates to an optical disk data reproducing method, and more particularly to an optical disk data reproducing method by which a reproducing operation is performed in accordance with track characteristics and recording system.
2. Discussion of the Background
Currently, recording media are mainly divided into magnetic disks and optical disks, and particularly the optical disks are in great demand due to its massive information storage capacity.
FIG. 1 illustrates a typical optical disk of which a radius L1 is 60 mm and a diameter of a center hall L2 is 15 mm. The optical disk has a main storage area (MSA), including a lead-in area and a lead-out area, and an outer area.
As shown in FIG. 4, the lead-in area includes a table of contents (TOC) which shows location information of a track or a recording system of an MPEG bit stream, and a data track of MSA includes a plurality of tracks (track 1, track 2, . . . , track N).
FIG. 2 is a schematic block diagram of a disk data reproducing device for the optical disk of FIG. 1.
As shown therein, the optical disk reproducing device includes an optical pickup 11 recording/reproducing data in an optical disk 10, a high-frequency amplifier 12 amplifying a reproduction signal outputted from the optical pickup 11, a digital signal processor (DSP) 13 digitalizing the amplified signal supplied from the high-frequency amplifier 12, and performing demodulation and error-correction of the signal, an MPEG decoder 14 decoding the signal outputted from DSP 13 a D/A converting unit 15 converting the signal outputted from the MPEG decoder 14 to an analog signal and outputting audio and video signals, an MPEG microcomputer 16 analyzing/judging the signal from the MPEG decoder 14, a microprocessor 17 performing a general control operation, a servo unit 18 performing a servo operation in accordance with control of the microprocessor 17, a memory 19 storing information which have been processed in the microprocessor 17, a display unit 20 displaying data, and a key input unit 21 receiving a key input signal from a user.
Now, the operation of the conventional optical disk data reproducing device will be described in detail with reference to FIGS. 2 and 3.
First, when a user reproduction instruction is supplied to the key input unit 21 after power is applied, the microprocessor 17 shifts the pickup 11 to the innermost part of the optical disk 10 and controls the servo unit 18, thereby performing focusing control and tracking control (S101, S103). When the pickup 11 is positioned on the innermost part of the disk 10, the microprocessor 17 controls the pickup 11 to move outward and determine whether the pickup 11 has reached the lead-in area of the MSA. (S105).
When the pickup 11 is in the lead-in area of MSA, the microprocessor 17 reads the TOC in the lead-in area (S107), and receives the TOC data which are passed through the high frequency amplifier 12, to determine if the MPEG data recorded in the track is NTSC or PAL based.
After recognizing the type of the MPEG data, the microprocessor 17 checks whether a reproduction location designating key has been inputted (S109). If the reproduction key is inputted, the microprocessor 17 shifts the pickup 11 to the designated position and reproduces an MPEG bit stream therefrom (S111). If not the microprocessor 17, reproduces the MPEG bit stream from the first end of the corresponding track (S113).
Next, when any reproduction location changing key is inputted over the key input unit 21 during the reproducing operation (S115), the microprocessor 17 shifts the pickup 11 to the location corresponding to the inputted reproduction location changing key and reproduces the MPEG bit stream from the changed track location (S117), and when the reproducing operation is completed or a reproduction interruption key is supplied from the user, the microprocessor 17 completes the reducing operation (S119).
The reproduced MPEG bit stream is amplified in the high-frequency amplifier 12, then the amplified MPEG bit stream is demodulated and error is corrected in the DSP 13 and the resultant bit stream is inputted to the MPEG decoder 14. The MPEG decoder 14 decodes the MPEG bit stream from the DSP 13 in accordance with parameters stored in the memory 21 and outputs the decoded MPEG bit stream to the D/A converting unit 15 and the microprocessor 17.
Thereafter, the D/A converting unit 15 converts the output signal from the MPEG decoder 14 to the analog signal and outputs the audio and video signals, and the MPEG microcomputer 16 analyzes/judges the output signal from the MPEG decoder 14 and outputs the result to the microprocessor 17, which processes various control operations on the basis of the output data from the MPEG microcomputer 16, and the process result thereof is stored in the memory 19 and also displayed on the display unit 20.
However, the conventional optical disk data reproducing method has a problem that video or audio data may not be normally reproduced when data of an optical disc in which information of the NTSC system and the PAL system coexist are reproduced by a scan or a random access or when characteristics of a present track are different from that of the previous track thereof, because the conventional optical disk data reproducing method uses information with respect to an NTSC or a PAL system until the completion time of the data reproducing operation without any change in the situation which either of the NTSC or PAL system is applied for recording data in an optical disk.
For example, when reproducing data of a track in which an NTSC bit stream is recorded by the scan or random access while data in the track in which a PAL bit stream is recorded are being reproduced, lower and upper parts of a picture may be cut off or the picture may be cracked.
Further, a hold in the picture may be occurred due to frame rate difference between the NTSC system and the PAL system.